If you reload, that is the fastest way to find an accurate load. I did that exact exercise for a DCRA rifle two weeks ago.
Get a quantity of good brass of the same lot number. Range pick up brass won't do.
Buy a box of 155 gr match bullets, or 168 gr if you are not planning on shooting beyond 300 yards.
Use a good powder, like 4895, Varget, N140 or RL15. Load 5 of each in 0.5 gr increments, from Start to Max, and shoot them at a good target, off a good rest.
One of the loads will look good. repeat the test with 20 of each with that load and 20 of each with 0.3 gr more and less.
In my DCRA rifle the very best loads were very mild. Good for up to 300 but not beyond.